Defending champion Marc Marquez claimed his second successive Grand Prix with victory in the Indianapolis MotoGP.
The 22-year-old Spaniard began on pole but was passed by compatriot Jorge Lorenzo on the opening corner.
Marquez, who won 13 of 18 races last year, seized the lead with three laps left for his third win of the season, climbing to third in the championship.
Valentino Rossi began eighth on the grid but finished third and leads Jorge Lorenzo by nine points.
"I'm very happy to only lose four points," said the Italian, who won the last of his seven world titles in 2009, and leads the standings with eight races left.
Marquez, who has moved above Italy's Andrea Iannone, is 56 points behind Rossi.
Lorenzo, world champion in 2010 and 2012, made a tremendous start but Marquez, yet to be beaten on American soil in MotoGP, set a new circuit lap record en route to Honda's 700th Grand Prix victory.
Marquez covered the 27-lap, 112.59km Indianapolis Motor Speedway course in 41 minutes, 55.371 seconds with Yamaha's Lorenzo, 0.688 seconds behind and has now won for the past five years at the venue in Moto2GP and MotoGP.
In the Moto3 race, Britain's Danny Kent, seeking to become the first Briton to win a world championship in any class since Barry Sheene in 1977, began on pole with a 76-point lead but as rain descended he finished 21st.
Livio Loi, the 18-year-old from Belgium, secured his first Grand Prix victory, with 21-year-old Scotsman John McPhee finishing second for his first podium finish in the competition. Kent still leads by 56 points with eight races remaining.
Alex Rins of Spain won the Moto2 race ahead of Johann Zarco, who is 71 points clear at the top of the standings. Britain's Sam Lowes did not finish and dropped two places to fifth in the standings.
Indianapolis Grand Prix results:
1. Marc Marquez (Spain) Honda 41 minutes 55.371 seconds
2. Jorge Lorenzo (Spain) Yamaha 41:56.059
3. Valentino Rossi (Italy) Yamaha 42:01.337
4. Dani Pedrosa (Spain) Honda 42:01.518
5. Andrea Iannone (Italy) Ducati 42:16.899
6. Bradley Smith (Britain) Yamaha 42:17.122
7. Pol Espargaro (Spain) Yamaha 42:25.749
8. Cal Crutchlow (Britain) Honda 42:26.978
9. Andrea Dovizioso (Italy) Ducati 42:28.192
10. Danilo Petrucci (Italy) Ducati 42:29.888
11. Maverick Vinales (Spain) Suzuki 42:34.381
12. Yonny Hernandez (Colombia) Ducati 42:37.186
13. Scott Redding (Britain) Honda 42:45.580
14. Aleix Espargaro (Spain) Suzuki 42:55.836
15. Hector Barbera (Spain) Ducati 42:59.518
MotoGP standings after race 10 of 18:
1. Valentino Rossi (Italy) Yamaha 195
2. Jorge Lorenzo (Spain) Yamaha 186
3. Marc Marquez (Spain) Honda 139
4. Andrea Iannone (Italy) Ducati 129
5. Bradley Smith (Britain) Yamaha 97
6. Andrea Dovizioso (Italy) Ducati 94
7. Dani Pedrosa (Spain) Honda 80
8. Cal Crutchlow (Britain) Honda 74
9. Pol Espargaro (Spain) Yamaha 73
10. Maverick Vinales (Spain) Suzuki 62
11. Danilo Petrucci (Italy) Ducati 57
12. Aleix Espargaro (Spain) Suzuki 46
13. Yonny Hernandez (Colombia) Ducati 36
14. Scott Redding (Britain) Honda 33
15. Hector Barbera (Spain) Ducati 20
Source: BBC Sport